1. Field of the Invention
This invention relates to a process for reducing the sulfane chain length of bis(silylorganyl)polysulfanes by reacting these compounds with a sulfide and a haloalkyl-silane.
2. Prior Art
Polysulfanes of this type have long been known (DE-PS 2255577) and are widely used as reinforcing additives in rubber vulcanisates containing silica, in particular in the tyre sector. Bis(triethoxysilylpropyl)tetrasulfane (Si 69, Degussa AG) has in particular become established in such applications (c.f. Wolff, 129.sup.th Meeting of the Rubber Division, American Chemical Society, Apr. 8-11, 1986, NY).
The processing advantages of corresponding disulfanes have recently been described in various publications. These compounds should be incorporated into the rubber compositions as the purest possible compounds according to EP-A-0732 362 (U.S. Pat. No. 5,580,919) or alternatively in the form of mixtures (DE-OS 197 0246.1).
However, according to the prior art, disulfanes are produced under unpleasant conditions as mercaptosilanes must be oxidised with manganese dioxide (EP-A 0718 302).